In this article the threshold gradient effect on short-duration well flow test analysis is investigated. The solutions, in a closed form, which are appropriate ta the pressure drawdown and buildup, are obtained for two cases of practical interest, namely wells producing from a circular closed reservoir and from a reservoir with constant pressure at the outer boundary.A comparison between the pressure responses obtained with and without the threshold gradient is presented in order ta illustrate this effect in ana-lysis of flow tests.As the results indicate, the threshold gradient effect is significant in some situations, and it should be considered in flow test analysis for correctly deter-mining porous medium properties from well data in producing reservoirs with a threshold gradient.